Colorimeters are devices for measuring the spectral content of light, where the measured light can be emitted either directly or indirectly from a given source. Recent developments have produced designs resulting in low cost colorimeters with performance characteristics approaching or exceeding professional quality required by the standards. One such colorimeter design is described in detail in U.S. Pat. No. 5,892,585, which is herein incorporated by reference in its entirety. With such cost effective, high-performance colorimeter designs available, a need has arisen for techniques for effectively mounting the colorimeter to the device being measured. In more detail, the physical factors relating to mounting a colorimeter to a target device present a number of non-trivial problems.
For instance, it is necessary to ensure that the forces of attachment are minimized to reduce pressure applied to a computer having a liquid crystal display (LCD). Otherwise, color distortion will occur. Also, LCD screens are particularly sensitive to the distribution and magnitude of the mounting forces. Thus, it is desirable that the colorimeter be relatively easy to position and attach to the target device. In addition, it is necessary to shield the measuring system from extraneous light (light from sources other than the target device being measured), which will otherwise reduce the signal-to-noise (SNR) ratio of the colorimeter system.
Conventional colorimeter designs employ a strap or hanging apparatus for securing or otherwise suspending the colorimeter in front of a display screen. A donut-shaped foam pad or similar soft pad is used to keep the colorimeter from pressing too hard on the screen so as to prevent color distortion. However, such designs are cumbersome to use due to the nature of the strap or hanging apparatus, and generally provide a significant impediment to simple user operation. In addition to the strap or hanging apparatus, such devices further require an electrical cable for carrying signals between the colorimeter and the host, which further contributes to area clutter and the cumbersome nature of such conventional designs. Moreover, such designs may not operate to maximize the SNR of the colorimeter device, particularly those designs where the colorimeter's peripheral field of view is not limited.
One such conventional colorimeter mounting design is described in U.S. patent application Ser. No. 10/251,426. In addition to an electrical cable for carrying signals between the colorimeter and the host, this particular design employs a mounting scheme having a suspension means to suspend the colorimeter in front of the monitor. The suspension means can be flexible (e.g., rubber tubing) or rigid (e.g., plastic). One end of the suspension means connects to the colorimeter, while the other end is connected to a counterweight.
Once the desired colorimeter position is achieved, the suspension means is secured into position by pressing it into slotted fulcrum device secured on the monitor to be measured. This leaves the colorimeter device in front of the monitor screen, and the counterweight hanging behind the monitor. Note, however, that the additional electrical cable must be managed during this balancing and positioning process, and ultimately introduces various stresses and twisting forces on the assembly. Such extra considerations further complicate the balancing and positioning process.
Other conventional mounting designs employ one to four relatively large suction cups to hold the colorimeter in place. One such device uses a large annular suction cup fitted about a color sensor, where the sensor measures through the center. Another such design uses a large rubber suction cup with a rigid clear member through which a proximate sensor can measure. Another such embodiment employs four large suction cups, one at each corner of the sensing device. These suction cup methods each suffer from reliability issues.
For example, if the seal fails due to an imperfection in materials or a particle of dust or debris, then air will leak into the cavity causing suction cup failure. With just one suction cup, the device will simply fall off the target being measured. With the four cup-corner type design, the weight of the device will be unevenly distributed, thereby causing a shift in alignment of the device and/or the failure of the remaining seals. This problem is further exacerbated in that displays have a tendency to attract dust. Moreover, the suction cups used in such designs have a relatively large depth. As a result, a slow air leak will cause the screen-to-sensor distance to substantially increase, thereby adversely affecting device measurement accuracy.
What is needed, therefore, are improved techniques for positioning and mounting a colorimeter to a target screen.